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/*******************************************************************************
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* Copyright (c) 2004, 2010 IBM Corporation and others.
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html
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*
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* Contributors:
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* IBM Corporation - initial API and implementation
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*******************************************************************************/
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package org.eclipse.draw2d;
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/**
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* Classes which implement this interface provide callback hooks for various
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* layout related events.
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* <P>
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* Instances can be hooked to figures by calling
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* {@link IFigure#addLayoutListener(LayoutListener)}. Listeners will be made
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* aware of various steps of the layout mechanism, and even have the opportunity
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* to prevent normal layout from occurring.
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*
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* @since 3.1
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*/
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public interface LayoutListener {
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/**
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* A stub implementation which implements all of the declared methods.
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*
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* @since 3.1
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*/
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class Stub implements LayoutListener {
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/**
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* Stub which does nothing.
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*
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* @see LayoutListener#invalidate(IFigure)
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*/
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public void invalidate(IFigure container) {
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}
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/**
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* Stub which does nothing.
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*
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* @see LayoutListener#layout(IFigure)
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*/
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public boolean layout(IFigure container) {
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return false;
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}
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/**
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* Stub which does nothing.
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*
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* @see LayoutListener#postLayout(IFigure)
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*/
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public void postLayout(IFigure container) {
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}
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/**
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* Stub which does nothing.
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*
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* @see LayoutListener#remove(IFigure)
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*/
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public void remove(IFigure child) {
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}
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/**
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* Stub which does nothing.
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*
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* @see LayoutListener#setConstraint(IFigure, java.lang.Object)
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*/
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public void setConstraint(IFigure child, Object constraint) {
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}
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}
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/**
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* Called when a container has been invalidated.
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*
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* @param container
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* the invalidated Figure
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* @since 3.1
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*/
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void invalidate(IFigure container);
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/**
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* Called prior to layout occurring. A listener may intercept a layout by
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* returning <code>true</code>. If the layout is intercepted, the
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* container's <code>LayoutManager</code> will not receive a layout call.
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*
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* @param container
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* the figure incurring a layout
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* @return <code>true</code> if the layout has been intercepted by the
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* listener
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* @since 3.1
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*/
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boolean layout(IFigure container);
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/**
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* Called after layout has occurred.
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*
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* @since 3.1
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* @param container
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* the figure incurring a layout
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*/
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void postLayout(IFigure container);
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/**
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* Called when a child is about to be removed from its parent.
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*
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* @since 3.1
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* @param child
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* the child being removed
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*/
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void remove(IFigure child);
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/**
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* Called when a child's constraint is initialized or updated.
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*
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* @param child
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* the child being updated
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* @param constraint
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* the child's new constraint
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* @since 3.1
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*/
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void setConstraint(IFigure child, Object constraint);
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}
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